The present invention relates generally to the field of acoustics, and in particular to transducers, to communication and power transmission using vibrations, and to taking sensor readings in deep wells.
The present invention includes improvements on the inventor's own previous work as described in International Patent Application PCT/US2013/056143 (published as WO2014/035785), U.S. Patent Application 61/693,366, and U.S. Patent Application 61/693,370, all of which are incorporated herein by reference, and which are intended for use with the present improvement and invention. These references disclose systems and methods for transmitting power and information using acoustic energy, typically through drilling and pipe systems. Pairs of acoustic wedges are provided for sending energy and information through a substrate. Typically the wedges will be acrylic and the substrate a metal. Each wedge has an angled transducer which is used to produce angled longitudinal waves which, upon reaching a substrate interface, produce shear waves (predominantly radial shear waves) in the substrate. Intermediate launch angles between upper and a lower critical angles are selected so that the longitudinal waves become shear waves on reaching the substrate. The shear waves propagate down the substrate and are received by a second acoustic wedge. The shear waves in the substrate transition back to longitudinal waves on reaching the second acoustic wedge, and they are converted back into electrical signals by a second transducer.
A transducer is a device that converts a signal in one form of energy to another form of energy. This can include electrical energy, mechanical energy, electromagnetic and light energy, chemical energy, acoustic energy, and thermal energy, among others. While the term “transducer” often refers to a sensor or a detector, any device which converts energy can be considered a transducer.
Transducers are often used in measuring instruments. A sensor is used to detect a parameter in one form and report it in another form of energy, typically as an electrical signal. For example, a pressure sensor might detect pressure—a mechanical form of energy—and convert it to electricity for display for transmission, recording, and/or as a power source. A vibration powered generator is a type of transducer that converts kinetic energy derived from ambient vibration to electrical energy.
A transducer can also be an actuator which accepts energy and produces movement, such as vibrational energy or acoustic energy. The energy supplied to an actuator might be electrical or mechanical, such as pneumatic or hydraulic energy. An electric motor and a loudspeaker are both actuators, converting electrical energy into motion for different purposes.
Some transducers have multiple functions, both detecting and creating action. For example, an ultrasonic transducer may switch back and forth many times a second between acting as an actuator to produce ultrasonic waves, and acting as a sensor to detect ultrasonic waves and converting them into electrical signals. Analogously, rotating a DC electric motor's rotor will produce electricity, and voice-coil speakers can also function as microphones.
Piezoelectric materials can be used as transducers to harvest even low levels of mechanical energy and convert them into electrical energy. This energy can be suitable for powering wireless sensors, low power microprocessors, or charging batteries. A piezoelectric sensor or transducer is a device that uses a piezoelectric effect to measure pressure, acceleration, strain, or force by converting those physical energies into an electrical charge. The piezoelectric effect is a reversible process in that materials exhibiting the direct piezoelectric effect (generation of an electrical charge as a result of an applied mechanical force) also exhibit the reverse piezoelectric effect (generating a mechanical movement when exposed to an electrical charge or field). Thus, piezoelectric transducers can also work in reverse, turning electrical energy into physical vibrational energy and vice versa. Piezoelectric transducers have the dual advantages of working using low energy levels, and a small physical size. Ultrasonic transducers may be piezoelectric transducers, applying ultrasound waves into a body, and also receiving a returned wave from the body and converting it into an electrical signal.
Ultrasonic transducers have been implemented with great success as sensors. U.S. Pat. No. 8,210,046 teaches a damper for an ultrasonic transducer mounted on a wedge body. Ultrasonic probes having phased array transducers inject acoustic waves into an object under test at an oblique angle to inspect the test object for flaws or defects. When the oblique angle is larger than the first critical angle, according to Snell's Law, the longitudinal waves will disappear, and only the newly converted shear waves will propagate in the object under test. A wedge with an angle larger than the first critical angle is usually attached to the transducer to generate shear waves in objects under test. Shear wave ultrasonic probes typically have a wedge body connected to the ultrasonic transducers on an angled surface relative to the wedge body surface that will contact an object under test, and a damping wedge fit over the front side of the wedge body opposite the transducers.
U.S. Pat. No. 3,542,150 describes an apparatus for gathering information about the earth surrounding a borehole using the device inside the borehole. Acoustic transducers are mounted at an angle with regard to the wall of the borehole wall or axis, and the traducers are mounted in a fluid coupling medium.
U.S. Pat. No. 4,454,767 teaches an ultrasonic metering device having two ultrasonic transducers mounted on wedges on opposite sides of the thickness of a pipe to measure the flow of fluid through that section of pipe.
U.S. Patent Application Publication No. 2010/0027379, by Saulnier et al., discloses an apparatus for communicating information across a solid wall having one or two outside ultrasonic transducers coupled to an outside surface of the wall and connected to a carrier generator for sending an ultrasonic carrier signal into the wall and for receiving an output information signal from the wall.
U.S. Patent Application Publication No. 2009/0045974, issued to Patel, discloses a downhole wireless communication method and system for a completed wellbore having a mother bore and two or more lateral branches, wherein at least one of the lateral branches is not electrically or hydraulically wet connected to the mother bore.
U.S. Pat. No. 4,893,496, issued to Bau et al., discloses a torsional wave fluid sensor and system. FIG. 10 illustrates a system employing a round pipe 260 and transducers 255, 256 with wedge blocks 257, 258 clamped to a pair of shoes 261, 262 that provide a flat face to hold transducers at the correct angle to launch obliquely refracted waves into the fluid. Flow in pipes is interrogated using waves in the pipe wall.
European Patent Application EP 0080789, by Tiede, discloses a wedge mounted acoustic emission sensor provided for continuously monitoring the stability of structural elements, such as bridges or buildings, by sensing the surface wave acoustic emissions in those structures, while rejecting acoustic emissions from sources outside the region of interest.
U.S. Pat. No. 2,844,741, issued to Murdoch, discloses producing and detecting ultrasonic beams of transverse/shear wave motion. A piezoelectric element is mounted on a wedge 11, which is disposed on first surface of a wedge 16. The second surface of the wedge 16 is placed in contact with surface of an object or specimen.
U.S. Pat. No. 3,512,400, issued to Lynnworth, discloses ultrasonic testing methods that employ Rayleigh waves to determine surface characteristic of a test specimen, Lamb waves that are a combination of longitudinal and shear wave components within a relatively thin plate of material, and Love waves in a coating.
U.S. Pat. No. 8,210,046, issued to Luo et al., discloses a composition for acoustic damping used for in damping wedges for ultrasonic probes.
Chinese Patent No. 101126741, issued to Ping et al., discloses longitudinal wave detection of a critical refraction component of tangential stress within a component auxiliary device.
U.S. Pat. No. 6,047,602, issued to Lynnworth, discloses ultrasonic flow measurement systems and particularly to wedges or buffer rods used to couple a transducer to a pipe or conduit wall for effecting a fluid measurement. The waveguide couples ultrasonic energy from a source on one side of a fluid-bounding wall, such as a conduit, into fluid on the other side of the wall.
In drilling and oil well operations, it is often necessary to communicate information (such as sensor data) along a drill pipe string. A drill pipe string consists of connected segments of piping. Often, portions of the well and drill string are not directly accessible via a direct electrical connection. For example, there may be segments that are disjointed and sealed off from each other, making electrical connection between the segments impossible. Since it is desirable to obtain data from deep within wells, passage of the data through these obstacles is a significant issue.
Transducers have been applied for communication between one another along oil wells and other boreholes. U.S. Patent 2001/0205080 describes communicating along a borehole by placing transducers on the borehole tubing, and sending acoustical signals between the transducers along the tubing itself. The receiver transducer operates on battery power. U.S. Patent No. 2011/0176387 describes a bi-directional acoustic telemetry system for communicating data and control signals between modems along a tubing. The systems includes a communication channel defined by the tubing material using a transducer at each model. There is still a need for improved systems, however.
Accordingly, one method and arrangement for powering, controlling, and communicating with sensors at a distance uses acoustic wave energy. The arrangement comprises a transmission arrangement comprising an acoustic signal generator, a receiving arraignment comprising an acoustic signal receiver, a least one sensor which is electrically coupled to the signal receiver, and a waveguide spanning between and engaged to the signal generator and the signal receiver. An acoustical wave preferably comprising a control signal can be generated with the signal generator, the acoustical wave preferably having sufficient strength to provide operating power to the sensor. The acoustical wave is transmitted from the signal generator to the signal receiver through the waveguide. The acoustical wave is received at the signal receiver, and converted into an electrical current optionally comprising a converted control signal. Preferably the electrical current is also used to power a sensor, communication device and/or other devices in the vicinity of the receiving arrangement. A control signal can simultaneously or alternatively be transmitted by the above method, such as by modulating the acoustic wave.
Transmitting and receiving arrangements can comprise piezoelectric transducers, where the signal generator piezoelectric transducer generates an acoustical wave comprising a control signal in response to electrical current applied to it. The signal receiver piezoelectric transducer then receives at least part of the acoustical wave, and converts at least a portion of the received acoustical wave into an electrical current which is then used to power and/or control the sensor. The sensor is not limited to any one sensor, and may detect pressure, temperature, vibrations, sounds, light, or other conditions.
It is possible to power one or more sensors exclusively using electricity generated by the signal receiver piezoelectric transducer, particularly sensors with low power requirements.
In one useful configuration, the transmission arrangement is above ground, while the receiving arraignment and a sensor are below ground, such as in a mine, well, tunnel, or shaft. Waves transmitted from the signal generator to the signal receiver through the waveguide can be used to power and control the sensor below ground. Waves in the reverse direction can transmit sensor data or other data back to the same transmission arrangement, or to a different arrangement provided for that purpose.
Waves can be modulated in a variety of known ways to create the control signal. In a preferred embodiment a continuous wave for transmitting power is selectively modulated when it is desired to send signals or information in addition to or instead of operating power.
A method of transmitting at least one of power and signals along a substrate using angle beam probes can include:
providing a transmitting acoustic wedge and a receiving acoustic wedge spaced apart on a substrate and coupled to the substrate at respective interfaces;
wherein each acoustic wedge comprises a transition wedge and a transducer comprising a transducer face, wherein the transducer is coupled to the transition wedge, and wherein a transducer face of each transducer is normal to an angle θ with regard to the substrate at the respective interface;
wherein, in some arrangements: the transducer face of the transmitting transducer of the transmitting acoustic wedge is normal to an angle θ1 with respect to the respective interface with the substrate, the angle θ1 in some embodiments between first and second critical angles such that longitudinal waves produced by the transmitting transducer are substantially converted into shear waves in the substrate;
in some arrangements the method further comprising producing longitudinal waves at angle θ1 at the transmitting transducer;
in some arrangements, the longitudinal waves producing substantially only shear waves in the substrate, and the shear waves propagating through the substrate until reaching the interface between the substrate and the receiving acoustic wedge;
in some arrangements, energy from the shear waves providing acoustical wave energy which reaches the receiving transducer of the receiving acoustic wedge; and
the receiving transducer converting at least a portion of said acoustical wave energy into electrical energy.
In alternative arrangements, shear waves created by angled longitudinal waves can be used to send power and/or signals down the length of a substrate such as a steel pipe in an oil well.
A transmitting acoustic wedge and a receiving acoustic wedge can be provided spaced apart on a substrate and coupled to the substrate at respective interfaces. In one embodiment each acoustic wedge comprises a transition wedge and a transducer comprising a transducer face. The transducer is coupled to the transition wedge, and a transducer face of each transducer is normal to an angle θ with regard to the substrate at the respective interface. A preferably planar transducer face of the transmitting transducer of the transmitting acoustic wedge is normal to an angle θ1 with respect to the respective interface with the substrate, the angle θ1 being between first and second critical angles such that longitudinal waves produced by the transmitting transducer are substantially converted into shear waves in the substrate.
One method further includes producing longitudinal waves at angle θ1 at the transmitting transducer. The longitudinal waves produce only or substantially only shear waves in the substrate, and the shear waves propagate through the substrate until reaching the interface between the substrate and the receiving acoustic wedge. Energy from the shear waves provides acoustical wave energy which reaches the receiving transducer of the receiving acoustic wedge, and the receiving transducer converts at least a portion of said acoustical wave energy into electrical energy. The energy can be used to transmit power and/or signals to sensors or other electronics. This is particularly useful for sensors and electronics deep underground.
In some arrangements, most or all of the shear wave energy which reaches the receiving acoustic wedge converts back to longitudinal waves at the receiving acoustic wedge. The receiving transducer of the receiving acoustic wedge then receives at least a portion of the longitudinal waves and converts at least a portion of said longitudinal waves into electrical energy.
In previously known arrangements, the substrate comprises metal(s) such as steel, and the transition wedges are acrylic. The substrate may be a metal pipe, such as in an oil well.
In some arrangements, wedge, transducer, and substrate methods and apparatus can also be used to send signals in the reverse direction from the receiving acoustic wedge to the transmitting acoustic wedge. The step of sending signals in the reverse direction comprises the receiving transducer generating waves at an angle with respect to the respective interface with the substrate, the angle being between first and second critical angles, and the waves propagating through the substrate to the receiving acoustic wedge.
In another arrangement, the transition wedge of the transmitting acoustic wedge includes a generally slanted edge which is normal to an angle θ1 with respect to the respective interface with the substrate. Typically a flat or planer face of a transducer is fixed to the slanted edge so that the transducer face is oriented in the same direction, i.e. on the same plane, as the slanted edge. In practice, the orientation of the transducer will often be selected by selecting a proper angle for the slanted edge. Thus, preferably, the slanted edge is normal to an angle θ1 is between first and second critical angles such that longitudinal waves produced by the transmitting transducer are substantially converted into shear waves in the substrate.
Though the substrate may be a large item with a large surface area and varied shape, the angle of the substrate where the respective acoustic wedges and transducers are located is a key angle of concern in selecting longitudinal wave angles. Typically this will be the angle at an interface between each acoustic wedge and the substrate.
Proper angles for launching longitudinal waves to produce shear waves in a substrate can be determined using Snell's law. The angle θ1 between first and second critical angles can be the longitudinal wave launch angle θ1Longitudinal. Thus, the method of the invention can include the step of determining θ1Longitudinal using the relationship:
      arcsin    ⁡          (                        V                      1            ⁢            Longitudinal                                    V                      2            ⁢            Longitudinal                              )        <      θ          1      ⁢      Longitudinal        <      arcsin    ⁡          (                        V                      1            ⁢            Longitudinal                                    V                      2            ⁢            Shear                              )      
wherein V1Longitudinal is the longitudinal wave speed in the transition wedge, V2Longitudinal is the longitudinal wave speed in the substrate, and V2Shear is the shear wave speed of the substrate. This is a method for determining the angle and orientation of the transducers and/or slanted edges supporting the transducers.
Longitudinal wave are waves where the displacement of the medium is in the same direction as, or the opposite direction to, the direction of travel of the wave. Mechanical longitudinal waves are also called compression waves, because they produce compression and rarefaction when traveling through a medium.
A shear or transverse wave is a moving wave that consists of oscillations occurring perpendicular (i.e. at right angles) to the direction of energy transfer. If a shear wave is moving in the positive x-direction, its oscillations are in up and down in the y-z plane. With transverse waves in matter, the displacement of the medium is perpendicular to the direction of propagation of the wave. A ripple in a pond or a wave on a string are examples of transverse waves.